/Engine/Source/Runtime/Core/Public/HAL/IPlatformFileOpenLogWrapper.h
Open a file for async reading. This call does hit the disk; it is synchronous open.
Close the file by delete'ing the handle. A non-null return value does mean the file exists. Null can be returned for many reasons even if the file exists. Perhaps this platform does not support mapped files, or this file is compressed in a pak file. Generally you attempt to open mapped, and if that fails, then use other file operations instead.
virtual [IMappedFileHandle](API\Runtime\Core\Async\IMappedFileHandle) * OpenMapped ( const TCHAR * Filename )